YSM Issue 90.4

low-density gas circling the galaxy, up to 30,000 light-years
from the galaxy core.
While it may seem that these high-powered inner-galactic
winds would quench the starburst phase of the galaxy,
slowing the rate of star production by blowing out much of
the hydrogen gas needed to create new stars, the researchers
suggest that the opposite is actually true. Transforming
previous models for galaxy formation, Falgarone and her
team propose that the winds actually extend the star-formation
phase by feeding these vast reservoirs of “fuel” for future
stars.
“What we have found with CH+ is that this stellar feedback
generates turbulence in the galactic environment, so energy
is lost and the outward momentum of the gas is lost too.
Indeed, most of the gas expelled from the galaxy eventually
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gas reservoir surrounding the galaxy but would like to see
some more data before making the conclusion that this
reservoir is what prolongs the starburst phase. “I don’t see
the jump personally between the data and the conclusions,”
Arce said. “This is not to say that the results are invalid in
any way —just that the beauty of the data could have perhaps
been more fully presented in a longer piece.”
Larson and Arce also both expressed excitement about
what Falgarone’s work means for future research into star
formation. We are currently seeing very exciting results
coming from the ALMA telescopes. They observe in the
millimeter and sub-millimeter wavelengths, so they’re useful
for observing dust and molecular-level matter such as CH+.
“This paper is an example of the great work people are doing
with the ALMA telescopes,” Arce said.
IMAGE COURTESY OF ESO
►An artist’s impression of how cold hydrogen gas fuels star production in distant starburst galaxies. The turbulent gases that surround the
galaxy extend far beyond outwards of the starbust core where stars are formed.
falls back on it, feeding further star formation instead of
quenching it,” Falgarone explains.
The study has, however, raised a few questions among relevant
academic circles. “The authors suggest that turbulence
in the outlying molecular gas slows down its infall and prolongs
star formation. To me, this seems plausible but unproven.
I don’t see how the generation of strong turbulence would
contribute to the fueling of a starburst; if anything, I would
expect it to inhibit gas infall,” said Richard Larson of the Yale
Astronomy Department.
Yale professor Héctor Arce, who is currently researching
star formation in the Milky Way galaxy, had similar questions
about the data. According to Arce, the CH+ indicates
massive outflows of gas from the center of the galaxies. He
agrees that this likely means that these outflows feed a cool
The work acknowledges that the mass outflow rates
caused by the winds alone do not completely account for
the extreme rates of star production. Something else, still
unknown, is nourishing these reservoirs. Falgarone and her
team suggest that perhaps this extra mass is produced by
galactic mergers or possibly accretion from streams of gas
that are sucked into the gravity of the galaxy.
Falgarone’s work sheds light on questions that have been
puzzling scientists for years—they have wondered, how did
starburst galaxies come by their extra fuel? We may now
have some answers, but the result also raises new questions.
What causes the hot, violent winds at the centers of certain
galaxies, powering the cool gas reservoirs? Why do some galaxies
have them and others do not? Astronomers continue to
scour the cosmos for answers.
www.yalescientific.org
October 2017
Yale Scientific Magazine
29